1. Technical Field
The present invention pertains to broken shear pin indicating systems for rotary snow blowers. More particularly, the present invention pertains to a broken shear pin indicating system which utilizes a proximity sensor to detect cessation of operation of the snow blower head cutter drum.
2. History of Related Art
Large rotary snow blowers are used to clear roads of heavy snow buildup. As a rotary snow blower travels down a road, the cutter drums in the front of the machine move the snow off the road and the snow blower blows it over to the side of the road. If something is buried within the snow, such as a guardrail, boulder, or stationary object, the rotary blower head cutter drums will be stopped from turning. When this occurs, an extraordinary load is placed on both the transmission and on the entire power train. Such loads on the power train could destroy extremely expensive power train equipment and disable the snow blower for extended periods of time.
In the snow blowers in the prior art, shear pins are located in the power train in order to protect it. The shear pins are used to transmit power from the rotating inner shaft to the snow blower head cutter drums. If an object is contacted by the snow blower head cutter drums, the shear pins simply break and the expensive drive train components are thereby protected.
The problem which faces most operators of front discharge rotary snow blowers is that little indication is provided to the operator when a shear pin breaks. Some experienced operators may actually sense a small jerk or a noise which indicates that a shear pin has broken. But if one of the rotating snow blower head cutter drums is still working, most operators will assume that the blower is operating properly because a steady stream of snow will continue to be blown from the snow discharge outlet.
Prior art systems which attempted to provide an indication to the operator that a shear pin had, in fact, broken, have utilized a mechanical flag or mechanical clanker system.
In the mechanical flag system, the continuous rotation of the snow blower head cutter drum holds a flag in a noticeable position such that once the snow blower head cutter drum ceased rotating, the flag would no longer be visible. Another system utilizes a mechanical clanker to provide an audible indication to the operator that the snow blower head cutter drum was rotating. When the clanking ceases, the operator is alerted that shear pins have broken and a snow blower head cutter drum has stopped rotating.
While the prior art systems were effective when working properly, their lack of operational sophistication often provided unreliable results. There is therefore a need in the art for a simple, reliable system which quickly provides an obvious indication that a shear pin in the drive system for the snow blower head cutter drums in a snow blower has, in fact, broken.
The present invention is a system and method for indicating that a shear pin has broken in a snow blower head cutter drum in a rotary snow blower. A drive box (angle gearbox) is located between the two snow blower head cutter drums on the front of the snow blower. This drive box provides rotational power to the two snow blower head cutter drums mounted on either side. Located adjacent to the drive box are two proximity sensors. The proximity sensors are used to detect the speed of the cutter drums. One is located on each side of the drive box between the drive box and the cutter drum under a removable protective cover.
The proximity sensors monitor the speed of each cutter drum by detecting the presence of and time between designated targets. The proximity sensors are set to focus on a designated target.
Each time a designated target passes the stationary proximity sensor, a timer is reset. When the shear pins are broken, the timer will start measuring time and then continue measuring time as long as it is not reset. This measured time is then compared to a predetermined time. If the measured time equals or exceeds the predetermined time, then an indication is provided that the snow blower head cutter drum has stopped rotating due to the fracture of a shear pin and a signal is sent to the operator in the cab of the snow blower. This proximity sensor system provides a simple, reliable method to quickly provide an obvious indication to the cab operator that a shear pin has broken.